The true incidence of zinc deficiency in the population of the United States is unknown because of a lack of reliable parameters for evaluating zinc status. Although severe zinc deficiencies have recognizable clinical features, mild deficiencies are more difficult to evaluate but may be critical in the development of a fetus or young child. The goal of this project is to explore the possibility of using saliva as a diagnostic tool. The first objective is to determine whether collection, storage, and analytical procedures have an effect on salivary zinc concentrations. The following factors will be tested, stimulus aids, method of cleaning oral cavity, water consumption, flow rate, sample volume, fatigue of salivating, food intake, variations over time, and storage and analytical conditions. The next objectives are to determine and compare the sensitivity of zinc in the supernatent and sediment of mixed saliva vs. parotid saliva and its relationship to current parameters of zinc status. A low zinc diet will be fed to 10 male subjects for 10 weeks; zinc supplements will be given the last 2 weeks to observe repletion. Subjects will be evaluated by a physical exam, urinalysis, a battery of standard biochemical and hematological tests, taste acuity and zinc loading tests and possible parameters of zinc status. Rats will also be fed a diet low in zinc that will be supplemented with graded levels of zinc. Pilocarpine-stimulated saliva will be collected and compared to tissue levels of zinc at the end of the six week period, and again after zinc repletion has been established. The next objective will be to establish and compare normal values and ranges of zinc and other minerals in saliva in a population of 100 healthy subjects. The final objective of the study will be to determine the reproducibility of salivary zinc levels in the same individual with repeated determinations under variable (free-living) and identical (controlled) diets. These studies should indicate the reliability of saliva as an additional assessment tool for evaluating mineral status.